As noted, policies for further testing to confirm anti-D, exclude other antibodies, and assess whether the anti-D is passive or immune vary among TS laboratories.
Even though patient A.D. had a negative antibody screen at 28 weeks and a positive antibody screen before the C-section with their current pregnancy, it appears to be anti-D from RhIG administration at 28 weeks, but some TS laboratories may set up a full antibody identification panel to confirm the presence of anti-D. Others would proceed straight to a mini-panel of red cells, specifically selected to exclude other clinically significant antibodies in the presence of anti-D, providing these criteria are met:
- Mother is Rh-negative and has been tested on two separate occasions.
- The laboratory has confirmed the administration of RhIG prophylaxis.
- The result of the current antibody screen is positive and typical of anti-D due to RhIG.
- There is no record or history of an unexpected antibody.
In this case, all criteria were met and a selected mini-panel was set up to confirm the presence of anti-D and exclude possible co-existing maternal antibodies, which may have implications for possible HDFN and for transfusion to both the mother and newborn.
A mini-panel of six selected red cells (rr, r'r, and r''r cells), along with a positive Ror control and an autocontrol were set up.